(368b) Sustainable Organosolv Pretreatment of Lignocellulosic Biomass in High Boiling Point Solvents

Research Interests: Sustainable processing of lignocellulosic biomass, biomass valorization, biomass to biofuels, sustainable/green chemistries, process decarbonization, renewable energy, lignin utilization, applications of supercritical fluids in materials synthesis, bio-based polymers, plastic recycling/upcycling

Teaching Interests: Green Chemistry, Transport Phenomena, Thermodynamics, Polymer/Biochemical Engineering, Chemical Reactor Design, Chemical Reaction Engineering, Separations

To ensure complete utilization of lignocellulosic biomass like lodgepole pine for biobased fuels and chemicals, pretreatment is usually carried out to separate the main components of the biomass namely: cellulose (40-60 wt%), hemicellulose (10-40 wt%) and lignin (15-30 wt%). In the traditional pulping industry, cellulose fibers are used in making paper, while the lignin generated is of low quality and is combusted to generate low-quality heat. However, since lignin could constitute up to 30 wt% of the material, and is the largest natural source of aromatics, it is finding applications in polymer blends, antioxidants, nanoparticles, and jet fuels. Hence the need for pretreatments that produce high-quality lignin and the development of organosolv pulping has helped in that regard. Organosolv pulping involves the use of organic solvents to break down lignin and dissolve it, leaving behind the cellulose fibers. The lignin can be recovered by solvent evaporation or the addition of water to the solution. However, most well-established organosolv processes utilize volatile organic compounds (VOCs), which not only require the use of specialized equipment because of their high vapors at temperatures required for effective pretreatment but also pose environmental concerns.

In the research, I investigate high boiling point solvents including polar aprotic ones like dimethyl sulfoxide (DMSO), 1,3-dimethyl-2-imidazolidinone (DMI), sulfolane (SUL), as well as three glycerol-derived solvents namely: 1,3-dimethoxypropanol (DMP) and 1,3-diethoxypropanol (DEP), as well as 1,2,3-triethoxypropane (TEP) as potential solvent candidates for biomass pretreatment, with the addition of organic superbase, sulfuric acid or acetic acid as catalysts. The impact of solvent speciation (DMSO, DMI, SUL, DMP, DEP, or TEP), concentration (0-100 vol%), reaction conditions (temperature 120-200 °C, batch time 10-60 min, sulfuric acid concentration 0-40 mN) are tested using the Klason lignin analysis method to quantify the extent of fractionation and delignification, surface morphology imaging using the scanning electron microscope (SEM) to understand changes in the surface features of the pine after pretreatment, spectroscopic analysis of the residual cellulose pulp to elucidate the removal of functionalities during pretreatment and appearance of functional groups in the precipitated lignin, X-ray diffraction to estimate changes in crystallinity of the residual pulps at different pretreatment conditions and 2D nuclear magnetic resonance imaging (NMR) to elucidate the structural features of the lignin precipitates. The goal is to help further develop the cocktail of renewable and eco-friendly solvents available for biomass fractionation/pretreatment.